The New Safe Confinement made simple

The New Safe Confinement

The New Safe Confinement (NSC) is a multipurpose complex for Shelter Object transformation into an environmentally safe system, consisting of 19 sub-structures, including the main one, which is an arch-shaped protective structure with a special double cladding, as well as specific foundations, West and East end walls, custom-made bridge cranes, a multipurpose ventilation system, a process complex with sites for decontamination, fragmentation and packing of radioactive materials, sanitary locks, workshops, back-up power supply system, fire fighting system, water treatment facilities, radiation monitoring system, seismic and structures monitoring system, communications and industrial TV system, CCTV, integrated control system, and other auxiliary systems and process premises. Therefore, the giant arch-shaped structure with a span of 257 m, 110 metres high (35-storeyed house) and 165 metres long (one and a half football field), and weighing more than 36 tons, better known as the Arch, is just a component of the complicated NSC system.


NSC as one of the Shelter Implementation Plan phases

It is a well-known fact that after the accident, the “Sarcophagus” or more correctly the Shelter object was erected, heroically and in the shortest possible time (206 days). The Shelter object is a facility made of concrete and steel, covering the remnants of the destroyed reactor.

Before the NSC

At the moment of the accident there contained almost 200 tons of nuclear fuel in the reactor, and after the explosion it transformed into the unbelievable amount of fuel-containing materials (FCM). Two pictures below show the amount of radioactive substances present inside the destroyed Reactor 4 and types of FCM in different premises.

As you can see, the dose rates in some points are still equal to thousands of roentgens (for example, 2050 R/h in room 505/3). Inside the Sarcophagus there still remains about 95% of the fuel, which was in the reactor at the moment of the accident.

Because of the highest construction rates and the use of remote methods for execution of some works in 1986, the sealing capacity of the Shelter leaves much to be desired: the total area of cracks in the roof and walls makes 1000 m2. Remote methods of installing the structures, and the inability to use welding to connect them made it impossible to define the object as a stable facility. The stabilization activities carried out in 2008 have reduced the risk of collapse of building structures, thus some level of stability of the Shelter has been achieved, but only till 2023. Further, it will be necessary either to stabilize unstable building structures or dismantle them. And finally, the lava-like fuel-containing materials contained within, gradually spontaneously disintegrate and transfer from a bound state into movable dust particles, therefore, there is a risk that in case of emergency collapse of the structures the radioactive dust could rise up and go with the air flow in any direction.

In accordance with the Memorandum of Understanding between the Governments of the G7 Countries and the Commission of the European Communities and the Government of Ukraine on the Closure of the Chornobyl Nuclear Power Plant, of December 1995, and within the TACIS project “Chornobyl unit 4. Short and Long Term Measures – Measures 2+4”, the Recommended action plan was developed. Further to the work on this project, Shelter Implementation Plan (SIP) was developed (adopted at the G7 meeting in June 1997) in cooperation of the European Union Commission (EC), Ukraine, the US and a group of international experts. The Plan identified the basic concept, including a number of moves aimed at bringing the Shelter object into an environmentally safe condition.

Development of SIP has marked the culmination of the efforts made by Ukraine and international community to develop an economically and environmentally acceptable approach to addressing the problems of Shelter of ChNPP Unit 4. Shelter Implementation Plan identified three phases as the key decisions for management and subsequent implementation of the project:
- Confirmation of the decisions on stabilization, identification of the possibility to perform previously proposed work on stabilization, including the provision of necessary access to the places of work and protection of staff in the performance of these works inside the Shelter object;
- Decision on the strategy for fuel containing materials (FCM), which will determine the optimum method and period for FCM retrieval with the justification of costs and the extent of the possibility to perform it;
- Decision on the strategy for the optimum localizing containment, which will identify its functions. Based on this decision and the FCM strategy, a conceptual design will be developed confirming the decision on stabilization, protection and the need for the localizing containment. Within SIP it was decided that construction of a huge Arch (NSC) over the Shelter would be the most optimum solution to contain the Shelter for the next century.

The first and the main NSC function is limiting the radiation effects of the Shelter on public, personnel and the environment both in normal operation and in case of emergency situations (for example, in case of collapse of the sarcophagus components due to their ramshackle state or during dismantling activities).

In case of any collapse of the Sarcophagus structural elements after the NSC is in its design position over the Shelter, the risen dust will remain inside the Arch. This is ensured by another engineering solution. If you take a look at the NSC in section, you can see that the Arch for some reason has two claddings – internal and external. The point is that throughout the NSC operation the dry and warm air will be pumped between these two claddings. It will be done in order to create overpressure that will prevent release of radioactive substances from the Arch to the environment. And the air should be dry and warm in order that condensation is prevented, and consequently the corrosion on the Arch steel (i.e. almost all) components. Car owners know well how expensive it is to keep a car in a dry garage, and how quickly it is destroyed in a damp place. And the Arch should stand for at least 100 years.

The second important NSC function is creating conditions for dismantling of unstable Shelter structures, as well as for removal and sorting of FCM and RAW, removal of accumulated water, and other works inside the Sarcophagus. What does it mean? It means that ideally, after the NSC is slid over the Sarcophagus, sealed and commissioned, we will be able, remotely using the already installed cranes system, a) to dismantle Sarcophagus roof, b) to reinforce what is unstable, c) to remove all other structures which can collapse, d) to start figuring it out what to do about all that radioactive mess contained inside the SO.

Another NSC function is physical protection of the Shelter from external intrusion of any kind. Moreover, it includes both the global threat of the earthquake, and simply an unauthorized access of strangers to the FCM and radioactive waste (RAW).

According to designers, NSC easily withstands tornado class 3 (these occur once every 1,000,000 years) and an earthquake of 6 points on MSK 64 scale (these occur once every 10,000 years, and Ukraine is located in a low seismic risk area), and finally the trivial temperature changes ranging from -43°С up to +45°С.

In addition, the Arch protects the FCM contained inside the SO from water ingress, wind, temperature drops and other destructive factors, transforming the FCM into dust. In other words, NSC preserves all the SO contents in a more or less stable condition.

According to the existing strategy based on the RAW management experience of other countries, all high-level waste which will be removed from the SO, should be processed and subsequently disposed in deep geological formations. And here a number of issues arise. Firstly, suitable deep formations are yet to seek in Ukraine. Secondly, in order to deliver HLW from ChNPP to these formations, it would be necessary to transport this waste using special vehicles on public roads. As for other RAW to be retrieved from SO, they should be processed at LRW Treatment Plant or at the Complex for SRW Management (liquid – to evaporate, solid – to incinerate and package, and then put into containers and pour concrete castings). In any case, after all necessary procedures, the amount of retrieved RAW could be easily multiplied by 3. Now take a look again at the picture with the amount of FCM inside the Shelter and tell WHICH geological formations are capable of housing such an amount of RAW? In line with the above mentioned, in-situ disposal is currently being considered, which proves that it is safer and more cost-efficiently to leave all the Sarcophagus’ contents inside the Sarcophagus following their preliminary sorting, analysis, inventory and monitoring.

There is one more problem. The point is that financing of the NSC project from the West finishes on the very first day of the NSC commissioning, that is in late 2017. Operation of the NSC is the financial problem of Ukraine only. Given the situation in the country, we can say that there is a chance of underfunding of not only dismantling activities inside the SO, but also of the NSC operation in the near future.

Who constructs
and finances
the Arch

Engineer is Project Management Unit (PMU) consisting of Bechtel (USA) – Bettelle Memorial (USA) – ChNPP.

Contractor, responsible for design, procurement and construction is NOVARKA consortium, comprising 2 French companies: VINCI Construction Grands Projets and Bouygues Travaux Publics.

The project is financed through the specially established Chornobyl Shelter Fund (CSF), managed by the European Bank for Reconstruction and Development (EBRD).

The total cost of the Arch amounts to EUR 1.5 bn.

The overall NSC construction time has made 10 years. The Contract was signed on 10 August 2007, on 29 October 2007 works commenced, and in November 2017 construction activities should be completed and the NSC should be put into pilot operation.

Construction involves professionals from contracting and sub-contracting organizations from 27 countries of the world. However, the basic amount of works is performed by 2,000 Ukrainian workers; more than 1,000 of them are constantly present at the site; 50 people at the site are engaged in radiation protection activities only.

Major sub-contractors:

- CIMOLAI – Italy: Working design and manufacturing of steel structures
- PaR – USA: Design and manufacturing of the Main Cranes System
- OKYANUS – Turkey: Design, supply and installation of cladding

How the Arch
was constructed

It all started with the incredible scope of preparatory work. 55 cubic meters of process materials and solid radioactive waste were removed from the future construction site only in order to start the construction.

When the Sarcophagus was erected, a large amount of contaminated materials of all sorts were put under ground right there, for there was nowhere and no time to transport that entire contaminated staff. As a result, the incredible amounts of earth excavated for site preparation were considered not as debris, but as radioactive waste, in addition a few vehicles and mechanisms were excavated.

The total of 396 steel piles, 376 reinforced concrete piles, and 8 thousand tons of re-bars were installed, 39 cubic meters of concrete was poured only in order to make temporary and permanent Arch foundations.

Then, when assembled, the two halves of the Arch were lifted separately using special jacks by Mammoet Company. The eastern part was lifted in October 2013 and moved on special rails 112 meters aside. Afterwards, in October 2014 the western part was lifted. Following the western part lifting, the eastern part was back-skidded, and both parts were joined together with the unbelievable number of bolts, and additional supports and side segments were also installed.

Bolts can be under tightened, over tightened, and perfectly tightened. When under tightened, there is a play, in the second case there is a stripped thread, and in the third case we have gratitude from management, and the safety ensured. For assembly of the Arch 650 thousand bolts were used. The cost of one bolt is about EUR 25.

Bolts of NSC

Together with the works in the Arch Erection area, Arch end walls are constructed – these are stable and fundamental structures to which NSC will be adjacent. Works are performed by Ukrainian contractors in very complicated radiation conditions inside the Shelter object.

Although the average dose rate in the NSC Erection area is not very high, many of the works which are performed on the Arch’s way to the final position, and especially in the designed stop position, are radioactively hazardous.

To ensure nuclear, radiation and general industrial safety, NSC Integrated Control System is being installed.

Fire Safety System, Physical Protection System are also installed, communication and TV lines are mounted. In order to ensure dismantling of unstable structures, crane equipment is mounted.

In November 2016 this giant will be slid on special rails and placed directly over the Sarcophagus.

Final works, sealing, and installation of auxiliary premises and equipment will be performed throughout the next year, and in December 2017 NSC will be put into test operation.

After the NSC is commissioned, the remnants of the destroyed power unit will still present some hazard, despite the new confinement. The Law of Ukraine “On the National Programme of Chornobyl NPP Decommissioning and Shelter Object Transformation into an Environmentally Safe System” provides for the Shelter transformation into an environmentally safe system by implementing a large range of measures. It is necessary to dismantle unstable Shelter structures, develop FCM retrieval process procedures, and remove and dispose all the RAW remaining in the Shelter. Dismantlement of unstable structures becomes the most burning issue, which should be resolved before the end of the established time limit of Shelter’s stability that is till 2023. However, these works are beyond the scope of works financed through the Chornobyl Shelter Fund, and the source of their financing has not yet been determined. The NSC operation costs will become a burden on the state budget of Ukraine, because in the active phase, according to preliminary estimates, they will exceed operating costs of the Shelter object roughly by 5 times and will amount to about $ 60 million. per year.

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